The present invention relates to an automatic door sensor. In particular, the present invention concerns measures to ensure an accurate detection operation of an object (e.g. a human body) located on the track of an automatic door, thereby enhancing the reliability of the opening and closing action of the automatic door.
Usually, with respect to an automatic door which opens and closes along a track, object detection ranges are set on the interior and the exterior of its doorway. Objects in these detection ranges are detected by an activation sensor. The activation sensor generally includes sensor mats, ultrasonic sensors and pyroelectric sensors. On detecting entry of an object into any of the detection ranges, the activation sensor performs an ON operation to open the door.
In addition to this activation sensor, an auxiliary sensor is disposed in the vicinity of the track of the door, between the interior and exterior detection ranges. As disclosed in Japanese Patent Laid-open Publication No. 2000-320243, for example, the auxiliary sensor makes use of light beams (e.g. infrared rays). Typically, the auxiliary sensor can be classified into three types.
The first type of auxiliary sensor is shown in FIG. 8. Beam sensors are mounted on a pair of posts 94 which stand on both sides of a doorway 93. Transmitters 95 on one of the posts are located face to face with receivers 96 on the other post (the structure in FIG. 8 employs two beam sensors, each of which is composed of a transmitter 95 and a receiver 96). In each sensor, when a light beam is emitted from the transmitter 95 towards the receiver 96 and interrupted by a person or the like, the receiver 96 fails to receive the light beam. The sensor regards this condition as the presence of an object near the track of doors 90. Based on this recognition, the auxiliary sensor holds the doors 90 open, even when the activation sensor is turned off.
The second type of auxiliary sensor is shown in FIG. 9. A transmitter 95 and a receiver 96 are mounted at the end of a first door 91, whereas mirrors 97 are provided at the end of a second door 92 in order to reflect the light emitted from the transmitter 95 back to the receiver 96. Similar to the first prior art structure, when a light beam is emitted from the transmitter 95 and interrupted by a person or the like, the receiver 96 fails to receive the light beam. The sensor regards this condition as the presence of an object near the track of the doors 91, 92. Based on this recognition, the auxiliary sensor holds the doors 91 and 92 open, even when the activation sensor is turned off. Such an auxiliary sensor is disclosed, for example, in Japanese Patent Laid-open Publication No. H6-138253.
The third type of auxiliary sensor is shown in FIG. 10. An ultrasonic sensor 99 is built in a transom 98 above a doorway 93 and produces ultrasonic waves to and around the track of doors 90. In FIG. 10, the detection area of the ultrasonic sensor 99 is indicated by a dash-dotted line. According to this sensor, a sensor signal from the ultrasonic sensor 99 is considered valid only when the doors 90 are fully open. On the other hand, when the doors 90 are fully closed or in the course of closing, any sensor signal from the ultrasonic sensor 99 is considered invalid. This principle prohibits the sensor 99 from wrongly detecting the closing doors 90 as a person or other object. Thus, the doors 90 are not opened at unnecessary occasions. Such an auxiliary sensor is disclosed, for example, in Japanese Utility Model Laid-open Publication No. H1-112287.
However, these conventional sensors have various problems as mentioned below.
As for the first type of auxiliary sensor, the transmitters 95 and the receivers 96 are mounted on the posts 94. Hence, this sensor is unable to direct the beams in a space vertically above the track, and may fail to detect an object which lies on the track. In other words, if an object locates at a position depicted by an imaginary line i in FIG. 8, the sensor cannot detect the object, which is high enough for the height position of the beams but which fails to block the beams. Furthermore, installation of the transmitters 95 and the receivers 96 involves a complicated wiring arrangement through the inside of the posts 94. Particularly, if a plurality of beam sensor sets are employed, the wiring arrangement is extremely complex and requires higher installation costs.
The second type of auxiliary sensor is capable of directing the beam in a space vertically above the track, and thus capable of detecting an object which lies on the track. However, installation of this sensor is more complex than that of the first type of sensor, because the transmitter 95 and the receiver 96 are mounted on the door 91, with the wiring led through the inside of the door 91.
The third type of auxiliary sensor can solve the problems concerning the first and second types of sensors. Nevertheless, the third type of sensor may make a wrong detection, owing to a change in the floor condition (e.g. a change of the reflection factor). For example, if the floor condition turns from dry to wet due to rainfall or the like, the sensor may wrongly recognize the change of the floor condition as the entry of a person. In this case, the doors 90 are left open even when no person is present on the track of the doors 90.
As mentioned above, none of the conventional automatic door sensors can perform fully reliable object detection operations in the vicinity of the track of the doors 90. Therefore, there has been considerable demand for an automatic door sensor which can ensure satisfactory reliability in object detection.
The present invention is made in view of such problems and demands. An object of the present invention is to provide an automatic door sensor which can accurately detect an object located in a predetermined area which is defined on or above the track of an automatic door, thereby enhancing the reliability of the opening and closing action by the automatic door.
In order to achieve the above object, the present invention employs a pair of sensors whose detection areas cross each other on the track or in a space vertically above the track. With such sensors, the recognition of an object (e.g. a person) that in located on the track takes place when both of the sensors produce detection signals. Thus, the present invention improves reliability in an object detection operation on the track. Besides, the crossed detection areas are utilized in determining the presence or absence of an object (e.g. a person). The resulting structure is less susceptible to adverse influences which may be caused, for example, by a change of the reflection factor on the floor.
Specifically, the present invention supposes an automatic door sensor which detects the presence or absence of an object on a track of an automatic door. This automatic door sensor comprises a pair of sensor means for detecting an object and producing an object detection signal, if the object is located within a detection area of each sensor means which is defined in a surrounding area of a doorway. The detection areas of the respective sensor means partially cross each other on the track or in a space vertically above the track as viewed from an extension direction of the track. The automatic door sensor also comprises control means which is capable of receiving the object detection signal produced by each of the sensor means. This control means recognizes the presence of an object on the track and keeps the door in an open state only when the control means receives the object detection signals from both of the sensor means.
According to this feature, when an object (e.g. a person) is present on the track, it means that the object locates in a region where the detection area of one of the sensor means crosses that of the other sensor means. In this situation, object detection signals are produced by both of the sensor means. On receiving the object detection signals from both sensor means, the control means keeps the door open, judging that an object is present on the track of the door. In the case of a conventional auxiliary sensor (e.g. the ultrasonic sensor shown in FIG. 10), the sensor may make a misoperation, for example, when a reflection factor on the floor changes. By contrast, in order to detect an object, the sensor of the present invention utilizes a region where the detection areas of both sensor means cross each other. To give an example, even if the detection area of either sensor means may become wet due to rainfall or the like, the sensor of the present invention does not determine the presence of an object as long as the condition of the other detection area remains unchanged. Consequently, this sensor is capable of properly distinguishing a change of the reflection factor on the floor from the presence of an object, and thus capable of conducting an accurate object detection operation.
With respect to the control operation of the control means, the control means is arranged to start an action for closing the door if the control means receives the object detection signal from only one of the sensor means uninterruptedly for a predetermined time. According to this feature, if the control means receives the object detection signal from only one of the sensor means for a predetermined continuous time, the control means recognizes the presence of an object which is located off the track and in its vicinity, but judges that there is no object on the track. According to this judgement, the control means closes the door, because the door may be closed without problem when an object (e.g. a person) is not on the track and is located in its vicinity. Thus, it is possible to prevent the door from being kept open unnecessarily for a long time.
As for the manner of disposing the respective sensor means, each of the sensor means is disposed on a transom at the doorway. Regarding the manner of defining the detection area, the detection area of each sensor means is defined by a region which extends through the doorway across the track and which reaches a space on the other side of the door.
In this respect, each of the sensor means may be disposed on a side surface or a bottom surface of the transom. Also, each sensor means may be mounted on a ceiling surface if the transom is integrated into the ceiling surface.
In addition, the detection area can be defined in the following two ways. Firstly, the detection area of one of the sensor means may cross that of the other sensor means, as viewed from a front of the door. Secondly, the detection area of one of the sensor means may not cross that of the other sensor means, as viewed from a front of the door.